kernel-PAE (x86-only): Contains a kernel with support for 64GB of memory on x86 systems through Physical Address Extensions (PAE). Only x86 CPUs that support PAE can run this kernel. This kernel is provided because x86 systems can't address more than 4GB of memory without PAE extensions.

1. Install kernel-PAE:

[root@server1 ~]# yum install kernel-PAE

2. Update grub.conf to boot from PAE kernel. After installing, vi /boot/grub/grub.conf and look for the line "default=..".

The value determines the default boot kernel and the sequence begins with 0. Review the kernel titles and update the default to the PAE kernel you installed (0 in my case below) and :wq